The present invention relates to a guide which can assist in inserting a circuit board into a Chassis and in particular to a guide which provides bidirectional guidance.
Many electronic devices include one or more circuit boards such as printed circuit boards (PCB""S) which are positioned in or with respect to a chassis or box. Examples from among the numerous types of electronic devices which have circuit boards provided in a chassis or a box, include computers such as personal computers, work stations, laptop computers, personal digital assistants, communication devices such as network routers, switches, bridges and the like, telephones, telefax machines, entertainment devices such as audio or video equipment and the like.
Typically the positioning of boards in a chassis is performed in a manner to couple electrical connectors or components of PCB to electrical signal sockets, traces or other connectors or components for providing signal communication to and from the board. One example is a board which include one or more pins extending therefrom, intended to be received in a pin block or receptacle having a plurality of sockets or regions for receiving the pins. Other examples of connections for printed circuit boards include edge connections (printed conductive lines or traces positioned on over or near the edge of the PCB) and like.
Insertion of boards into a chassis or a box may be performed in a number of situations including during initial fabrication of an electrical device, during testing, repair or replacement of the electrical device or components thereof, during ordinary maintenance, upgrading or modification of an electrical device (which may, in many cases, be performed by a substantially untrained end user).
Typically, for proper functioning the electronic device, the board or boards must be properly aligned with the corresponding blocks so that the pins or other electrical connectors mate with the correct sockets.
Many older circuit boards included a relatively a small number of pins or connectors such as fewer than about 800 pins per board, often fewer than about 500 pins per board. The total number of pins, as well as the size of the board and the design of the board (which can determine where, on the board, the pins may be positioned) place constraints on the density of the pins and thus on the size or diameter of the pins. Older boards, with relatively fewer pins, could be configured with pins having a relatively large diameter, i.e. which were sufficiently sturdy that the force imparted to the pins as a result of misalignment of the board with respect to the pin block, as the board is being inserted, could be tolerated by the pins and, indeed, in such a situation, the pins themselves can function to guide the board into the desired orientation with respect to the pin block or similar connector.
As designs of electronic devices have evolved, circuit boards have been developed having a relatively larger number of pins, such as over 1,000, and in some cases over 1,400 pins, in such a fashion that the spatial density of the pins in at least some parts of the board, require pins of relatively smaller diameter, in particular, of diameters such that the pins are relatively delicate and may be unable to withstand the forces resulting from a somewhat misaligned board insertion process without bending, breaking or other undesirable deformation or damage to one or more pins. Accordingly, it would be useful to provide a procedure and apparatus which can reduce misalignment between a board and a pin block, or otherwise reduce misalignment between pins and pin sockets (or other electrical connectors) so as to reduce or avoid pin damage.
Some previous systems have provided structural (non-signal carrying) pins and sockets coupled respectively to circuit boards and chassis for assisting in alignment. However, many such devices are believed to provide relatively loose alignments which, while possibly suitable for larger-diameter pins, may be ineffective in reducing or preventing damage to relatively small-diameter pins. Additionally, it is believed that at least some previous alignment or guidance devices provided guidance along or with respect to one axis or plane, without achieving substantial guidance (and especially, without achieving close-tolerance guidance) with respect to a second non-parallel (typically orthogonal) axis or plane. Accordingly, it would be useful to provide a guidance device and procedure which can provide guidance in two non-parallel (preferably orthogonal) axes or planes, and preferably with a relatively tight spacial tolerance (high accuracy) such as a tolerance, in at least one direction of about 0.02 inches (about 0.5 mm), or less, preferably about 0.015 inches (about 0.3 mm), or less.
In some configurations, linear tracks or shelves were used for providing a degree of guidance, e.g. to board side-edges, i.e. edges parallel to the direction of board insertion. While such tracks or shelves can be useful in assisting board insertion, such tracks or shelves typically provide relatively loose guidance and typically provide guidance only in a single plane or axis (i.e. provides unidirectional guidance) and/or are spaced a relatively large distance from other, possibly pin-bearing, edges (such as an edge perpendicular to the side-edges), thus providing little guidance or support to edges of the card which may be pin-bearing edges. Such side-edge guidance or support may be insufficient to overcome gravitational or other sag-inducing forces, at least because the shelves or tracks are spaced from the central (possibly pin-bearing) region of the board where gravity-induced sag may be greatest. Such gravitational sag can be particularly troublesome for relatively larger boards (such that the side-edge supports or guides are relatively distantly positioned with respect to the middle of the board) and/or having relatively small diameter pins (such that even relatively small amounts of sag can have pin-damaging results. Sag-induced or other misalignment can be particularly difficult to correct or overcome when card insertion is performed by grasping and manipulating a card edge which is the edge that is opposite the pin-bearing edge (as is commonly the case) and in which there may be little or no close-tolerance guidance provided for the pin-bearing edge itself, such that even small movements or angular displacements at the grasping edge may result in relatively large movements or displacements at the distant pin-bearing edge. Accordingly, it would be useful to provide a board guidance procedure and method which can provide guidance in a region of the board spaced from the board side edges, such as at or near central regions of the pin-bearing edges. It would be useful to provide a device which can provide sufficient guidance to avoid or reduce pin damage in spite of gravitational sag.
Many electronic devices are configured to contain two or more different circuit boards and require, for proper functioning, that a circuit board be positioned only in a single (or a few) predetermined slot or other location, i.e. are intolerant of interchanging the positions of two or more boards. However, many chassis and/or board guidance devices are configured to receive any of a number of different boards in each location, relying on the knowledge, dexterity and accuracy of the person installing the boards. Accordingly, it would be useful to provide an apparatus and procedure which can prevent at least some or all instances of board mis-location (i.e. positioning a board in the wrong slot or other location). Preferably, in order to reduce the number of components in the electronic device, it would be advantageous to provide such board-positioning assurance as a function or component of the board guidance devices or systems.
For a guidance system to be useful for achieving alignment of pins or board components with pin blocks or other receptacles or connectors, it is, in general, useful to provide for relative alignment of the guidance components with respect to the pin blocks or other receptacles. In many situations, the cost of fabricating or manufacturing devices increases as the amount of required alignment precision increases. The amount of alignment precision, as noted above, can be particularly acute when circuit boards are provided with relatively delicate, small-radius pins. Accordingly, it would be useful to provide a board insertion guidance system which can be implemented with the desired degree of positional precision without unduly increasing the cost or complexity of the design, manufacture or assembly of the electronic device.
Another factor which can affect the cost of an electronic device is the efficiency with which components and/or circuitry can be positioned on various circuit boards. Accordingly, it would be useful to provide a guidance and/or mislocation lockout device and procedure which has a high degree of flexibility with respect to designing circuitry or components for a circuit board (e.g. which can be located in a range of positions on or with respect to the circuit board) and/or which is relatively small (i.e. which requires relatively little reduction in the amount of circuit board surface available for circuitry or components and/or connector pins).
The present invention provides a device and/or system by which a guide member interdigitates or otherwise engages with a shape, such as a cutout, recess or other shape, formed on the pin-bearing edge or connector-bearing edge of a circuit board. In one aspect, the chassis-mounted guide includes a web which is inserted into a slot or cutout formed in the pin-bearing edge of the circuit board. Beveling or chamfering of the leading edge of the web provides a lateral guiding or camming force to assist in moving or positioning the circuit board in the desired lateral direction (i.e. a direction parallel to the pin-bearing edge). The provision of relatively close tolerance between the size of the web and the size of the cutout, over a length of the web, assists in providing angular guidance, such that the pin-bearing edge is brought parallel to the pin block.
Preferably a (e.g. second) guide surface, substantially perpendicular to the plane of the web, engages a major surface (such as the bottom surface) of the circuit board to provide a transverse guidance force (i.e. in a direction substantially perpendicular to the plane of a major surface of the board). By beveling or chamfering the region adjacent the leading edge of the second guide surface, a guidance or camming force acts on the board near the pin-bearing edge in a fashion so as to guide the pins into transverse alignment with the pin block. In one embodiment, the second surface chamfer is large enough to allow the second guide surface to engage a major surface of the circuit board even when the circuit board is somewhat deformed from a strictly planar shape, such as being deformed by gravitational sag, (e.g. when the circuit board is in a horizontal or other non-vertical position during insertion).
In one embodiment, a circuit board recess or cutout is positioned in different locations (such as different positions along the pin-bearing edge of the circuit board) for different circuit boards, and a web or guidance member is positioned correspondingly on the chassis. In this way, the guidance member or web member will prevent full insertion of the wrong circuit board since, preferably, a circuit board other than the intended or proper circuit board will not have a cutout in circuit board which is positioned (or sized or shaped) to engage or receive the web or guide member.